Package comprising radar chaff



Dec. 7, 1965 E. a. PAQUETTE 3,221,375

PACKAGE COMPRISING RADAR CHAFF Filed July 2, 1965 INVEN TOR.

Lame 6. P49 :77: BY 6% A l;

United States Patent 3,221,875 PACKAGE COMPRISING RADAR CHAFF Elmer G.Paquette, Cambridge, Wis., assignor to the United States of America asrepresented by the Secretary of the Air Force Filed July 2, 1963, Ser.No. 293,236 3 Claims. (Cl. 206-65) This invention relates to packages ofparallel strands and to a method of making such packages. Moreparticularly, this invention relates to bundles of strands which may bedispensed into the atmosphere, as chaff or rope, to provide radarreflective dipoles to confuse enemy radar. Such bundles may be ofparallel lengths of metal strands, or of strands made of metalizeddielectric fibers.

In addition to solid metal fibers, such fibers may be made from vitreousmaterial such as glass or vitreous silica, and coated with a conductivemetal such as aluminum, magnesium or copper. Such fibers may be from onemicron to 200 microns in diameter, but are generally about to microns indiameter. The metallic coating, which is to be active as a dipole, isusually applied to be from 2 to 100 microns in thickness.

Electromagnetic radiation of a frequency which is reso nant with thedipole, is reinforced by resonance in the dipole, and the radiation is,in effect, rebroadcast by the dipole. In effect, each dipole acts as areflector. The radiation emanating from a plurality of dipoles which areresonant with the frequency emitted from an enemys radar apparatusappears on the oscilloscopes of the radar as a bright cloud or a brightobject having various characteristics depending on the manner in whichthe dipole material is dispensed. Such dipole material, having a lengthof from Mi inch to about 1 /2 inches is referred to as chaff. Materialwhich is longer than about 1 /2 inches, and which may be up to say 500feet in length, but is preferably from about 3 inches to 100 feet inlength, is referred to as rope.

Rope is not intended to be resonant with radar frequencies; but isintended to respond to other frequencies, or to effectively emitradiation at other frequencies in response to frequencies to which it isnot resonant. It is generally preferred to dispense a certain amount ofrope and a certain amount of chaff of various lengths, more or lesssimultaneously. This invention provides chaff, packaged in convenientform, for ready dispersion in the atmosphere after being dispensed froman airplane.

It is therefore an object of this invention to provide chaff, inimproved bundles, for ready dispersion in the atmosphere.

Another object of this invention is to provide bundles of radar chaff inwhich the strands or fibers are relatively more parallel than has beenpossible heretofore.

Yet another object of this invention is to provide such bundles whichare more compact and more tightly compressed than has been possible inthe past.

Still another object of this invention is to provide such bundles whichare not enclosed with a vapor barrier and which therefore may breathe.

A further object of this invention is to provide such bundles in whichthe parallel strands are retained in the bundle by wrapping the bundlewith one or more strands in lieu of sheets or strips as heretofore.

A still further object of this invention is to form a bundle of radarchaff which is Wrapped with one or more strands of the same materialforming the chaff itself.

Additional objects, advantages and features of the invention reside inthe construction, arrangement and combination of parts involved in theembodiment of the invention as will appear from the followingdescription and accompanying drawing wherein:

FIG. 1 is a schematic illustration of a preferred man- 3,221,875Patented Dec. 7, 1965 ner of making wrapped bundles of strands fromwhich the radar chaff or rope is formed;

FIG. 2 is a perspective of one bundle of radar chaff in accordance withthis invention and having fine pitch wrapping, and

FIG. 3 is a perspective of one end of another bundle of strands formingrope, and having coarse pitch wrapping.

Referring now to FIG. 1, it will be presumed that the radar chaffbundles are to be formed of metalized fiber glass strands which havebeen wrapped by wrapping machine 10. A plurality of individual glassstrands 12, which had been drawn from a body of molten glass and coatedwith metal in any suitable manner, are converged and fed through acollector ring 14 from which they emerge in the compacted bundle form12a. The circularly compacted strands are then passed longitudinallythrough the hollow shaft motor 15 and emerge from disk 16. Disk 16 isjoined to and is rotated, in the direction indicated, by motor 15.

One or more rotatable spools 18, carrying nonadhesive wrapping thread 20are supported by and rotate with disk 16. The thread is spirally wrappedonto the strands as they are longitudinally drawn, without rotation, byroller 22 and roller 24 which is driven by motor 26 through belt 28. Itis well understood that the pitch of the thread encompassing the strandswill be a function of the linear travel of the strands and the rate atwhich disk 16 is caused to rotate.

Thread 20 may conveniently be of glass, either fine or coarse, and mayconsist of twisted and plied glass yarn or of strands of roving. Whetherclosely or widely spaced, the spiral wrapping does not form a vaporbarrier. The weight of the thread forming the wrapping can besubstantially less than that of the paper used on an equivalent roll.

The product leaving wrapping machine 10 may be cut to any suitablelength chaff or rope in various manners well known to the art. FIG. 2depicts a typical bundle of relatively short length strands to be usedas chaff. FIG. 3 depicts a broken end portion of the same strands cut toproper length for use as rope. When used as chaff, the thread 20 iswrapped to have a fine pitch, as shown in FIG. 2, and when used as ropethe thread is wrapped to have a coarse pitch as shown on FIG. 3.

The glass thread is obviously as temperature resistant as the fibersthemselves, and assumes no set whatever. For making transverse cuts, thewrapping has the same cutting characteristics as the material which itconfines and shows no tendency to snag and tear. For longitudinalslitting, the wrapping is much easier parted than a felted or wovencovering. It may be slit with almost any kind of cutting edge or evenwith a heated wire loop; and when slit at one point along thecircumference of the roll, it fully releases the contents. Metalizedfiber may be used as thread for the wrapping instead of bare glass. Thegain in efficiency of the chaff, if any, is insignificant, and itappears that for most purposes a rather fine strand of glass textilestock is most desirable.

The strands 12 may be of glass, metal, metalized, glass, syntheticfiber, or natural fiber including paper, twisted or untwisted, plied orunplied, and formed of staple or monofilamentary fibers. Likewise, thethread forming the wrapping may be made of any material suitable for thestrands, or may be tapes of woven or unwoven fabric, metal, paper,plastic film or other material. By varying the passage through thecollector ring to suit, in addition to the substantially cylindricalbundle shown, bundles may be produced having oval, square, triangular,or any other cross-sectional configuration.

It is to be understood that the embodiment of the present invention asshown and described is to be regarded as illustrative only and that theinvention is susceptible to variations, modifications and changes withinthe scope of the appended claim.

I claim:

1. A package of radar chalf comp-rising: a plurality of metallic coateddielectric strands having a selected length of from A inch to 1 /2inches formed into a longitudinal bundle and a wrapping of adhesion-freethread spirally wound and longitudinally encompassing said bundle ofstrands, said thread being of a dielectric material.

2. A package of radar chaff comprising: a plurality of metallic coatedfiber glass strands having a selected length of from /1 inch to 1 /2inches formed into a longitudinal bundle and a wrapping of threadspirally wound and longitudinally encompassing said bundle of strands,said thread being a fiber glass strand.

3. A package of radar chafi' comprising: a plurality of metallic coatedfiber glass strands having a selected length of from 4 inch to 1 /2inches formed into a longitudinal bundle and a wrapping of threadspirally wound and longitudinally encompassing said bundle of strands,said thread being a metallic coated fiber glass strand.

References Cited by the Examiner UNITED STATES PATENTS 2,238,727 4/1941Glassford 57-18 2,430,358 11/1947 Merwin et al. 57-18 2,516,212 7/1950Hoffmann et al. 573 2,572,052 10/1951 Pheazey 57--3 3,029,586 4/1962Walsh et a1 57--3 3,049,080 8/1962 Schermuly 102-37.6

LOUIS G. MANCENE, Primary Examiner.

SAMUEL FEINBERG, Examiner.

1. A PACKAGE OF RADAR CHAFF COMPRISING: A PLURALITY OF METALLIC COATEDDIELECTRIC STRANDS HAVING A SELECTED LENGTH OF FROM 1/4 INCH TO 1 1/2INCHES FORMED INTO A LONGITUDINAL BUNDLE AND A WRAPPING OF ADHESION-FREETHREAD SPIRALLY WOUND AND LONGITUDINALLY ENCOMPASSING SAID BUNDLE OFSTRANDS, SAID THREAD BEING OF A DIELECTRIC MATERIAL.